Julia Roberts has expanded her NYC apartment holdings by purchasing a penthouse co-op at 45 W. 10th St. for $3.895 million. The actress is also holding onto her Gramercy Park home, even though she spends much of her time in California and New Mexico.

Roberts’ new building in Greenwich Village has a rooftop terrace and is the only co-op on a coveted block between Fifth and Sixth avenues that mainly consists of single-family homes. It was built in 1958 on the site of the Tenth Street Studio Building, the nation’s first architectural school, where many Hudson River School painters had studios.

When reached by phone, Roberts’ spokeswoman declined to comment.

Thiel deal

His heart and primary home might be in San Francisco, but technology investor Peter Thiel, a Facebook billionaire and PayPal co-founder, is also renting a three-bedroom apartment at 15 Union Square West. The unit has 16-foot-high ceilings and custom finishes by designer Vicente Wolf.

While Thiel is renting for an undisclosed price, 15 Union Square West is known for its pricey condos, which typically go for more than $2,500 per square foot.

Thiel, an avowed libertarian who works as a venture capitalist and hedge-fund manager, made headlines last month when he announced that he would create a Thiel Fellowship to give 20 people under 20 years old $100,000 each to drop out of college and launch their own start-ups.

Butler did it

Gerard Butler is on the prowl again.

The actor recently checked out a $7.995 million townhouse condo at 385 W. 12th St. and also saw the building’s rooftop infinity pool. The four-bedroom, 3½-bathroom unit is 4,337 square feet and has a 575-square-foot garden off the formal living room. It was listed at $8.75 million in 2007, sold for $6.975 million last year and is now back on the market.

Brown Harris Stevens broker Reid Price could not be reached for comment.

Leavingstein

Ad man Alan Levenstein, former vice chairman at Bozell Worldwide, and his wife, Gail, who ran the private-client division at Bill Blass for many years, have put their 2,200-square-foot, second-floor co-op at 75 Central Park West on the market for $4.25 million.

The unit, in a classic Rosario Candela-designed building, includes a private elevator landing, a woodburning fireplace, a formal dining room and lots of unique built-ins. But its biggest selling point might be its views of Central Park from the double-sized living room, library and master bedroom.

Building residents have included controversial talk-show host Don Imus, writer Jimmy Breslin and the late actor Carroll O’Connor.